Transformers exist in which gaps that are substantially equal in width to a flattened rectangular conductor are provided between layers of two edgewise coils 1a, 1b. The flattened rectangular conductor layers of the edgewise coils 1a, 1b are individually assembled into the gaps so as to be alternately mounted to the core, thereby reducing leakage inductance and enhancing coupling properties. In such transformers, insulation reinforcement is performed on the flat wires (Patent Document 1).
Transformers also exist that are formed by attaching, to four corners on a core 1 contact side of a core 1, a spacer 2 that is provided with notches so as to conform to the corners of the core 1. Flat wires of a primary winding 3 and a secondary winding 4 wound in coil shapes are interposed such that one cross-section length direction end thereof is inserted into a comb shaped recess portion provided to a side face of the spacer 2 that retains the winding.
In the transformer described above, the primary winding 3 and the secondary winding 4 are retained at a specific separation by projection portions of the spacer 2. Moreover, the windings are insulated from and retained at a separation to the core 1 by a main body portion of the spacer 2. An increase in temperature of the transformer can moreover be suppressed by flowing cooling air between the windings themselves and between the windings and the core 1.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2004-103624    Patent Document 2: JP-A No. 2006-147927